Operation control device for air conditioner

ABSTRACT

A receiver (4) is provided in a main line (9a) and a bypass passage (4a) having an open/shut-off valve (SV) is provided for introducing gas refrigerant in the receiver (4) into a low-pressure liquid line. A motor-operated expansion valve (5) is fully closed, the open/shut-off valve (SV) is opened, and then defrosting operation is executed. At the initial stage of the defrosting operation, the open/shut-off valve (SV) is closed. When a discharge-pipe temperature Td drops to or below a specified temperature, the open/shut-off valve (SV) is closed. When the discharge-pipe temperature Td rises to or above a specified temperature, the motor-operated expansion valve (5) is once opened to a specified opening. When defrosting operation is completed, the open/shut-off valve (SV) is opened in a heating cycle and the motor-operated expansion valve (5) is gradually opened.

TECHNICAL FIELD

This invention relates to an operation control device for airconditioner, and particularly relates to measures for controlling theair conditioner during defrosting operation and for controlling the airconditioner just after completion of defrosting operation.

BACKGROUND ART

There has been a conventional air conditioner which is so composed thatan indoor unit is connected to an outdoor unit in which a compressor, afour-way selector valve, a thermal-source-side heat exchanger, amotor-operated expansion valve and a receiver are sequentiallyconnected, as disclosed in Japanese Patent Application Laid-Open GazetteNo. 4-344085. The air conditioner performs defrosting operation when afin of the thermal-source-side heat exchanger is frosted in heatingoperation.

Further, the defrosting operation is executed in a cooling cycle with anon-shown motor-operated expansion valve of the indoor unit and themotor-operated expansion valve of the outdoor unit fully openedtogether.

Problems to be solved

However since the above air conditioner is provided with an accumulatoron a suction side of the compressor in order to prevent operation in wetcondition of the compressor, the motor-operated expansion valves arefully opened in the defrosting operation so that operation performanceis decreased due to pressure loss at the accumulator.

If the accumulator is not provided to solve the above problem, since thedefrosting operation with the motor-operated expansion valves fullyopened, this causes liquid refrigerant condensed by thethermal-source-side heat exchanger to store in the receiver in the caseof heavy frost, low open-air temperature or short refrigerant piping.Thus, an amount of heat required for defrosting is lacked so that theliquid refrigerant in the receiver turns back to the compressor. Thisinvites operation in wet condition of the compressor, so that thecompressor is under stress. As a result, the reliability of thecompressor is reduced.

In view of the foregoing problems, this invention has been made. Anobject of this invention is to enhance operation performance without anyaccumulator while avoiding the compressor from operating in wetcondition in defrosting operation.

DISCLOSURE OF INVENTION

To achieve the above object, measures instituted in this invention areso composed as to execute defrosting operation while introducing gasrefrigerant in a receiver into a main line through a bypass passage.

Constitution

More specifically, as shown in FIG. 1, a measure instituted in theinvention premises an air conditioner comprising a refrigerant circuit(9) which has a main line (9a) in which a compressor (1), athermal-source-side heat exchanger (3), an expansion mechanism (5)freely adjustable in opening and a used-side heat exchanger (6) aresequentially connected and which is reversibly operable between coolingcycle operation and heating cycle operation.

A receiver (4) is provided in a high-pressure liquid line of the mainline (9a) of the refrigerant circuit (9). There is provided a bypasspassage (4a), which is connected at one end thereof to the receiver (4)and at the other end to a low-pressure liquid line of the main line (9a)of the refrigerant circuit (9), for bypassing the expansion mechanism(5) to introduce gas refrigerant in the receiver (4) into thelow-pressure liquid line.

Further, the bypass passage (4a) is provided with open/shut-off means(SV) for opening and shutting off the bypass passage (4a).

In addition, there is provided defrosting executing means (11) formaking the expansion mechanism (5) fully closed and making theopen/shut-off means (SV) open according to a defrosting requiring signalin the heating cycle operation and executing defrosting operation in thereverse cycle.

A further measure instituted in the invention comprises initial controlmeans (12) for outputting an initially closing signal to the defrostingexecuting means (11) so that the open/shut-off means (SV) is closeduntil a set time passes after the start of the defrosting operation.

A further measure instituted in the invention comprises wet conditioncontrol means (13) for outputting a closing signal to the defrostingexecuting means (11) so that the open/shut-off means (SV) is closed whena refrigerant temperature on a discharge side of the compressor (1)drops to or below a specified temperature.

A further measure instituted in the invention is so composed that thewet condition control means (13) outputs a closing signal so that theopen/shut-off means (SV) becomes an opened state after holding a closedstate for a set time, and then outputs an opening holding signal to thedefrosting executing means (11) so that the open/shut-off means (SV)holds the opened state for a set time after closed.

A further measure instituted in the invention comprises superheatingcontrol means (14) for outputting respective signals for opening andclosing the motor-operated expansion valve (5) to the defrostingexecuting means (11) so that when a refrigerant temperature on adischarge side of the compressor (1) rises to or above a specifiedtemperature, the expansion mechanism (5) is opened to a specifiedopening and then closed into a fully closed state.

A further measure instituted in the invention is so composed that thesuperheating control means (14) outputs a full-close holding signal tothe defrosting executing means (11) so that the expansion mechanism (5)holds the fully closed state for a set time after opened and closed.

A further measure instituted in the invention comprises operationsifting means (15) for shifting the circuit to heating cycle operationwhen the defrosting executing means (11) completes the defrostingoperation, so as to control the open/shut-off means (SV) to hold it openfor a set time in a heating cycle and then turn it closed whilecontrolling the expansion mechanism (5) to gradually open it to aspecified opening.

In further measure instituted in the invention, the bypass passage (4a),the open/shut-off means (SV) and the defrosting executing means (11) aresubstituted by respective other means. More specifically, in one measureinstituted in the invention, there is provided a bypass passage (4a),which is connected at one end thereof to the receiver (4) and at theother end to a high-pressure side of the expansion mechanism (5) of therefrigerant circuit (9), for introducing gas refrigerant in the receiver(4) into the high-pressure side of the expansion mechanism (5).

Further, there is provided selector means (V2) switchable between abypass communication state in which the high-pressure side of theexpansion mechanism (5) is communicated with the bypass passage (4a) anda main line communication state in which the high-pressure side of theexpansion mechanism (5) is communicated with the high-pressure liquidline of the main line (9a).

In addition, there is provided defrosting executing means (11A1) forswitching the selector means (V2) to the bypass communication state andopening the expansion mechanism (5) according to a defrosting requiringsignal and executing defrosting operation.

On the other hand, in another measure instituted in the invention, thereis provided a bypass passage (4a), which is connected at one end thereofto the receiver (4) and at the other end to a low-pressure liquid lineof the main line (9a) of the refrigerant circuit (9), for bypassing theexpansion mechanism (5) to introduce gas refrigerant in the receiver (4)into the low-pressure liquid line.

Further, there is provided selector means (V2) switchable between abypass communication state in which the low-pressure liquid line of themain line (9a) is communicated with the bypass passage (4a) and a mainline communication state in which the low-pressure liquid line of themain line (9a) is communicated with the low-pressure side of theexpansion mechanism (5).

In addition, there is provided defrosting executing means (11A2) forswitching the selector means (V2) to the bypass communication stateaccording to a defrosting requiring signal in the heating cycleoperation and executing defrosting operation.

Another measure instituted in the invention comprises, instead of theinitial control means (12) of the invention, initial control means(12A1) for outputting an initially closing signal to the defrostingexecuting means (11A1) so that the expansion mechanism (5) holds a fullyclosed state until a set time passes after the start of the defrostingoperation.

On the other hand, a further measure instituted in the inventioncomprises, instead of the initial control means (12) of the invention,initial control means (12A2) for outputting an initially closing signalto the defrosting executing means (11A2) so that until a set time passesafter the start of the defrosting operation, the selector means (V2)holds the main line communication state and the expansion mechanism (5)holds a fully closed state.

Further, a further measure instituted in the invention comprises,instead of the previously mentioned wet condition control means (13),wet condition control means (13A1) for outputting a fully closing signalto the defrosting executing means (11A1) so that the motor-operatedexpansion valve (5) is fully closed when a refrigerant temperature on adischarge side of the compressor (1) drops to or below a specifiedtemperature.

On the other hand, a further measure instituted in the inventioncomprises, instead of the previously mentioned wet condition controlmeans (13), wet condition control means (13A2) for outputting a fullyclosing signal to the defrosting executing means (11A2) so that when arefrigerant temperature on a discharge side of the compressor (1) dropsto or below a specified temperature, the selector means (V2) is switchedto the main line communication state and the expansion mechanism (5) isfully closed.

Furthermore, another measure instituted in the invention is so composedthat the wet condition control means (13A1) outputs a fully closingsignal to the defrosting executing means (11A1) so that the expansionmechanism (5) is opened after holding a fully closed state for a settime, and then outputs an opening holding signal to the defrostingexecuting means (11A1) so that the expansion mechanism (5) holds theopened state for a set time after fully closed.

Moreover, a further measure instituted in the invention so composed thatthe wet condition control means (13A2) outputs a switching signal to thedefrosting executing means (11A2) so that the selector means (V2) isswitched to the bypass communication state after the expansion mechanism(5) holds a fully closed state for a set time, and then outputs aswitching holding signal to the defrosting executing means (11A2) sothat the selector means (V2) holds for a set time the bypasscommunication state switched from the main line communication state fora set time.

A further measure instituted in the invention comprises, instead of thepreviously mentioned superheating control means (14), superheatingcontrol means (14A1) for outputting a first and second switching signalto the defrosting executing means (11A1) so that when a refrigeranttemperature on a discharge side of the compressor (1) rises to or abovea specified temperature, the selector means (V2) is first switched tothe main line communication state and then switched again to the bypasscommunication state.

On the other hand, a further measure instituted in the inventioncomprises, instead of the previously mentioned superheating controlmeans (14), superheating control means (14A2) for outputting a first andsecond switching signal to the defrosting executing means (11A2) so thatwhen a refrigerant temperature on a discharge side of the compressor (1)rises to or above a specified temperature, the selector means (V2) isfirst switched to the main line communication state while the expansionmechanism (5) is opened and then the selector means (V2) is switchedagain to the bypass communication state.

A further measure instituted in the invention is so composed that thesuperheating control means (14A1) outputs a switching holding signal tothe defrosting executing means (11A1) so that the selector means (V2)holds for a set time the bypass communication state switched from themain line communication state.

Further, a further measure instituted in the invention is so composedthat the superheating control means (14A2) outputs a switching holdingsignal to the defrosting executing means (11A2) so that the selectormeans (V2) holds for a set time the bypass communication state switchedfrom the main line communication state.

Operations

Under the above structure, when the defrosting executing means (11)starts defrosting operation in a reverse cycle according to a defrostingrequiring signal, it makes the open/shut-off means (SV) open whilemaking the expansion mechanism (5) fully closed.

Otherwise, the defrosting executing means (11A1) switches the selectormeans (V2) to the bypass communication state and fully opens theexpansion mechanism (5). Alternatively, the defrosting executing means(11A2) switches the selector means (V2) to the bypass communicationstate. Then, in such conditions the defrosting executing means (11,11A1, 11A2) circulates gas refrigerant in the receiver (4) into the mainline through the bypass passage (4a) thereby executing defrostingoperation.

Further, at the initial stage of the defrosting operation, theopen/shut-off means (SV) is closed while the selector means (V2) isswitched to the main line communication state and the expansionmechanism (5) is fully closed. In other words, both the main line (9a)and the bypass passage (4a) are shut off thereby preventing turning backof liquid refrigerant from the receiver (4).

Then, in the case where a refrigerant temperature on a discharge side ofthe compressor (1) drops to or below a specified temperature in thedefrosting operation, the open/shut-off means (SV) is closed, while theselector means (V2) is switched to the main line communication state andthe expansion mechanism (5) is fully closed. In other words, sinceliquid refrigerant in the receiver (4) may turn back to the compressor(1), both the main line (9a) and the bypass passage (4a) are shut offthereby preventing turning back of liquid refrigerant from the receiver(4).

Subsequently, the open/shut-off means (SV) is held in an opened statefor a set time after it is closed. Otherwise, the selector means (V2) isswitched from the main line communication state to the bypasscommunication state and the expansion mechanism (5) is held in an openedstate for a set time. Alternatively, the selector means (V2) is switchedfrom the main line communication state to the bypass communication stateand is held in this state for a set time. In other words, it isprevented to excessively execute opening/closing operation of theopen/shut-off means (SV) and the expansion mechanism (5) and switchingoperation of the selector means (V2), thereby avoiding operation insuperheated condition of the compressor (1).

On the other hand, in the case where a refrigerant temperature on adischarge side of the compressor (1) rises to or above a specifiedtemperature in the defrosting operation, the expansion mechanism (5) isopened, the selector means (V2) is switched to the main linecommunication state and then switched back to the bypass communicationstate, or otherwise the selector means (V2) is switched to the main linecommunication state while the expansion mechanism (5) is opened and thenthe selector means (V2) is switched back to the bypass communicationstate. In other words, liquid refrigerant in the receiver (4) is turnedback so that the superheated refrigerant temperature is decreased,thereby preventing operation in superheated condition of the compressor(1).

Subsequently, the expansion mechanism (5) is held in the fully closedstate for a set time after opened and closed while the selector means(V2) is held in the bypass communication state switched from the mainline communication state for a set time. In other words, it is preventedto excessively execute opening/closing operation of the expansionmechanism (5) and switching operation of the selector means (V2),thereby avoiding operation in wet condition of the compressor (1).

Thereafter, when the defrosting operation is completed, theopen/shut-off means (SV) is held in an opened state for a set time andis then closed while the expansion mechanism (5) is gradually opened,thereby preventing turning back of liquid refrigerant while ensuring theminimum circulation amount of refrigerant, so that heating cycleoperation is restarted.

Effects

Since gas refrigerant in the receiver (4) is introduced into the mainline (9a) through the bypass passage (4a) in the defrosting operation,when liquid refrigerant condensed in the thermal-source-side heatexchanger (3) is stored into the receiver (4) in the case of heavyfrost, low open-air temperature or short refrigerant piping, liquidrefrigerant in the receiver (4) can be securely prevented from turningback to the compressor (1) without provision of any accumulator. As aresult, operation in wet condition of the compressor (1) is securelyprevented so that the compressor (1) is subjected to no stress, therebyenhancing reliability of the compressor (1).

Further, since no accumulator is needed, pressure loss can be decreasedthereby enhancing operation performance, and the number of elements arereduced thereby resulting in cost reduction.

Since both the main line (9a) and the bypass passage (4a) are shut offat the initial stage of the defrosting operation, it can be securelyprevented that liquid refrigerant in the receiver (4) flows into thethermal-source-side heat exchanger (3) and the used-side heat exchanger(6) due to variation in pressure of the refrigerant circuit. Thus,turning back of liquid refrigerant to the compressor (1) can beprevented and a condensation area in the thermal-source-side heatexchanger (3) can be sufficiently ensured, so that defrostingperformance can be increased.

Since both the main line (9a) and the bypass passage (4a) are shut offwhen a refrigerant temperature on a discharge side of the compressor (1)drops in the defrosting operation, liquid refrigerant on a suction sideof the compressor (1) can be evaporated. Consequently, turning back ofliquid refrigerant can be prevented so that operation in wet conditionof the compressor (1) can be securely prevented, thereby furtherenhancing reliability of the compressor (1).

Further, since communication With the bypass passage (4a) is held for aset time after both the main line (9a) and the bypass passage (4a) areshut off, the compressor (1) can be prevented in advance from operationin superheated condition due to frequent shutting-off control of therefrigerant circuit.

When a refrigerant temperature on a discharge side of the compressor (1)rises in the defrosting operation, the expansion mechanism (5) is openedand communication is established in the main line (9a). Thus, liquidrefrigerant is turned back to cool down superheated refrigerant on asuction side of the compressor (1), so that operation in superheatedcondition of the compressor (1) can be securely prevented therebyfurther enhancing reliability of the compressor (1).

Further, since communication with the bypass passage (4a) is held for aset time once the expansion mechanism (5) is opened, the compressor (1)can be prevented in advance operation in wet condition due to frequentcommunication control of the main line (9a).

When the defrosting operation is completed, the open/shut-off means (SV)is opened and the expansion mechanism (5) is gradually opened. Sincethis ensures the minimum circulation amount of refrigerant at the shiftto heating operation, heating performance can be increased. Further,since turning back of liquid refrigerant to the compressor (1) can beprevented, operation in wet condition of the compressor (1) can beprevented while dilution of lubricating oil in the compressor (1) can beprevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the structure of the presentinvention.

FIG. 2 is a refrigerant circuit diagram showing an embodiment of theinvention.

FIG. 3 is a schematic diagram showing a receiver.

FIG. 4 is a timing chart showing the control of defrosting operation.

FIG. 5 is a refrigerant circuit diagram showing another embodiment ofthe invention.

FIG. 6 is a refrigerant circuit diagram showing another embodiment ofthe invention.

FIG. 7 is a refrigerant circuit diagram showing another embodiment ofthe invention.

FIG. 8 is a refrigerant circuit diagram showing another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, embodiments of this invention will be described with reference tothe drawings.

Embodiment 1

FIG. 2 shows a refrigerant piping system of an air conditioner applyingthis invention, which is a so-called separate type one in which a singleindoor unit (B) is connected to a single outdoor unit (A).

The outdoor unit (A) comprises a compressor (1) of scroll type to bevariably adjusted in operational frequency by an inverter, a four-wayselector valve (2) switchable as shown in a solid line of FIG. 2 incooling operation and in a broken line of FIG. 2 in heating operation,an outdoor heat exchanger (3) as a thermal-source-side heat exchangerwhich functions as a condenser in cooling operation and as an evaporatorin heating operation, and a pressure reduction part (20) for reducingrefrigerant in pressure. The outdoor heat exchanger (3) is provided withan outdoor fan (3f).

In the indoor unit (B), there is disposed an indoor heat exchanger (6)as a used-side heat exchanger which functions as an evaporator incooling operation and as a condenser in heating operation. The indoorheat exchanger (6) is provided with an indoor fan (6f).

The compressor (1), the four-way selector valve (2), the outdoor heatexchanger (3), the pressure reduction part (20) and the indoor heatexchanger (6) are sequentially connected through refrigerant piping (8),thereby forming a refrigerant circuit (9) in which circulation ofrefrigerant causes heat transfer.

The pressure reduction part (20) includes a bridge-like rectificationcircuit (8r) and a common passage (8a) connected to a pair of connectionpoints (P, Q) of the rectification circuit (8r). In the common passage(8a), there are arranged in series a receiver (4), which is placed in anupstream-side common passage (8X) serving as a high-pressure liquid lineat any time, for storing liquid refrigerant, an auxiliary heat exchanger(3a) for outdoor heat exchanger (3), and a motor-operated expansionvalve (5) freely adjustable in opening, which serves as an expansionmechanism having a function of reducing liquid refrigerant in pressureand a function of adjusting a flow rate of liquid refrigerant.

Another pair of connection points (R, S) of the rectification circuit(8r) are connected to the indoor heat exchanger (6) side of therefrigerant piping (8) and the outdoor heat exchanger (3) side of therefrigerant piping (8) respectively. There is formed a main line (9a) inwhich the compressor (1), the four-way selector valve (2), the outdoorheat exchanger (3), the rectification circuit (8r) and the commonpassage (8a) are sequentially connected and the rectification circuit(8r), the indoor heat exchanger (6), the four-way selector valve (2) andthe compressor (1) are sequentially connected.

Further, the rectification circuit (8r) is provided with: a first inflowpassage (8b1) which connects the up-stream-side connection point (P) ofthe common passage (8a) to the connection point (S) on the outdoor heatexchanger (3) side and has a first non-return valve (D1) for allowingrefrigerant to flow only in a direction from the outdoor heat exchanger(3) to the receiver (4); a second inflow passage (8b2) which connectsthe upstream-side connection point (P) of the common passage (8a) to theconnection point (R) on the indoor heat exchanger (6) side and has asecond non-return valve (D2) for allowing refrigerant to flow only in adirection from the indoor heat exchanger (6) to the receiver (4); afirst discharge passage (8c1) which connects the down-stream-sideconnection point (Q) of the common passage (8a) to the connection point(R) on the indoor heat exchanger (6) side and has a third non-returnvalve (D3) for allowing refrigerant to flow only in a direction from themotor-operated expansion valve (5) to the indoor heat exchanger (6); anda second discharge passage (8c2) which connects the downstream-sideconnection point (Q) of the common passage (8a) to the connection point(S) on the outdoor heat exchanger (3) side and has a fourth non-returnvalve (D4) for allowing refrigerant to flow only in a direction from themotor-operated expansion valve (5) to the outdoor heat exchanger (3).

Between both the connection points (P, Q) of the common passage (8a) ofthe rectification circuit (8r), a liquid seal preventing bypass passage(8f) provided with a capillary tube (C) is formed. The liquid sealpreventing bypass passage (8f) prevents liquid seal at the deactivationof the compressor (1). Further, between the upper part of the receiver(4) and a part of the downstream-side common passage (8Y) which islocated on a downstream side of the motor-operated expansion valve (5)and serves as a low-pressure liquid line at any time, there is providedan open/shut-off valve (SV) as open/shut-off means connected to a bypasspassage (4a) for bypassing the motor-operated expansion valve (5),thereby venting gas refrigerant stored in the receiver (4).

In detail, as shown in FIG. 3, the receiver (4) is connected at a bodycasing (41) thereof to the upstream-side common passage (8X), thedownstream-side common passage (8Y) and the bypass passage (4a). Thedownstream-side common passage (8Y) is introduced into an inner bottompart of the body casing (41) in order that liquid refrigerant isdischarged therefrom. The bypass passage (4a) is connected to the upperpart of the body casing (41) in order that gas refrigerant is dischargedtherefrom.

The degree of pressure reduction of the capillary tube (C) is set at asufficiently larger value than the motor-operated expansion valve (5) sothat the motor-operated expansion valve (5) adequately maintains thefunction of adjusting a flow rate of refrigerant in normal operation.

(F1 to F4) indicate filters for removing dusts from refrigerant, and(ER) indicates a silencer for reducing operational sound of thecompressor (1).

The air conditioner is provided with various sensors. (Thd) is adischarge pipe sensor, which is disposed in a discharge pipe of thecompressor (1), for sensing a discharge-pipe temperature Td as arefrigerant temperature on a discharge side of the compressor (1). (Tha)is an outdoor inlet sensor, which is disposed in an air inlet of theoutdoor unit (A), for sensing an outdoor-air temperature Ta as anopen-air temperature. (Thc) is an outdoor heat-exchange sensor, which isdisposed in the outdoor heat exchanger (3), for sensing an outdoorheat-exchange temperature Tc as a condensation temperature in coolingoperation and as an evaporation temperature in heating operation. (Thr)is an indoor inlet sensor, which is disposed in an air inlet of theindoor unit (B), for sensing an indoor-air temperature Tr as a roomtemperature. (The) is an indoor heat-exchange sensor, which is disposedin the indoor heat exchanger (6), for sensing an indoor heat-exchangetemperature Te as an evaporation temperature in cooling operation and asa condensation temperature in heating operation. (HPS) is ahigh-pressure-control pressure switch for sensing a pressure ofhigh-pressure refrigerant and turning on at the excessive rise inpressure of high-pressure refrigerant to output a high-pressure signal.(LPS) is a low-pressure-control pressure switch for sensing a pressureof low-pressure refrigerant and turning on at the excessive drop inpressure of low-pressure refrigerant to output a low-pressure signal.

Respective output signals of the sensors (Thd to The) and the switches(HPS, LPS) are inputted into a controller (10). The controller (10) isso composed as to control air conditioning according to the inputsignals.

In the above-mentioned refrigerant circuit (9), circulation ofrefrigerant in cooling operation is made in the following manner.Refrigerant is condensed in the outdoor heat exchanger (3) so as to beliquefied. Liquid refrigerant thus liquefied flows through the firstnon-return valve (D1) from the first inflow passage (8b1), is thenstored in the receiver (4), is reduced in pressure by the motor-operatedexpansion valve (5), flows through the first discharge passage (8c1),and is evaporated in the indoor heat exchanger (6). Refrigerant thusevaporated returns to the compressor (1). On the other hand, circulationof refrigerant in heating operation is made in the following manner.Refrigerant is condensed in the indoor heat exchanger (6) so as toliquefied. Liquid refrigerant thus liquefied flows through the secondnon-return valve (D2) from the second inflow passage (8b2), is thenstored in the receiver (4), is reduced in pressure by the motor-operatedexpansion valve (5), flows through the second discharge passage (8c2),and is evaporated in the outdoor heat exchanger (3). Refrigerant thusevaporated returns to the compressor (1).

The controller (10) sections an operational frequency of the inverterinto 20 steps N from zero to the maximum frequency, controls thecapacity of the compressor (1) by finding out each frequency step N sothat the discharge-pipe temperature Td becomes an optimum discharge-pipetemperature, and controls the opening of the motor-operated expansionvalve (5) so that the discharge-pipe temperature Td becomes an optimumdischarge-pipe temperature.

The controller (10) has, as a feature of this invention, a defrostingexecuting means (11), an initial control means (12), a wet conditioncontrol means (13), a superheating control means (14) and an operationshifting means (15).

The defrosting executing means (11) is so composed as to make themotor-operated expansion valve (5) fully closed and make theopen/shut-off valve (SV) open according to a defrosting requiring signaloutputted when the refrigerant circuit (9) becomes specified conditionsand to execute defrosting operation in the reverse cycle.

For example, the controller (10) memorizes the sum of heatingperformance from the start of heating operation after the end ofdefrosting operation, divides the sum of heating performance by theperiod of time that a heating operation period after the end ofdefrosting operation and a defrosting operation period to be preliminaryexpected are added to calculate a mean value of heating performance, andoutputs a defrosting requiring signal when the mean value of heatingperformance is below the last-time mean value of heating performance.

In any one of the case that the frequency step N of the compressor (1)drops to 6, the case that the discharge-pipe temperature Td rises above110° C. and the case that the defrosting operation period becomes longerthan 10 minutes, the defrosting executing means (11) completes thedefrosting operation.

The initial control means (12) outputs an initially closing signal tothe defrosting executing means (11), until a set time passes from thestart of the defrosting operation, e.g., until 15 seconds pass, so as tomake the open/shut-off valve (SV) closed, thereby closing therefrigerant circuit (9) for 15 seconds.

The wet condition control means (13) outputs a closing signal forclosing the open/shut-off valve (SV) to the defrosting executing means(11), so that when the discharge-pipe temperature Td of the compressor(1) drops below a specified temperature, e.g., 85° C., the open/shut-offvalve (SV) holds a closed state for a set time and then becomes anopened state, e.g., for 20 seconds. Further, the wet condition controlmeans (13) outputs an opening holding signal to the defrosting executingmeans (11) so that the open/shut-off valve (SV) holds for a set time theopened state after closed, e.g., so that the open/shut-off valve (SV)holds the opened state for 30 seconds by activating a timer for 50seconds after the output of the closing signal.

The superheating control means (14) outputs respective signals foropening and closing the motor-operated expansion valve (5) to thedefrosting executing means (11), so that when the discharge-pipetemperature Td of the compressor (1) rises above a specifiedtemperature, e.g., 90° C., the motor-operated expansion valve (5) isopened to a specified opening and then closed into a fully closed state.In other words, the superheating control means (14) once opens themotor-operated expansion valve (5) of a fully closed state to apartially opened state of 200 pulses, in which a fully opened state ofthe motor-operated expansion valve (5) is indicated as 480 pulses, andthen fully closes it. Further, the superheating control means (14)outputs a full-close holding signal to the defrosting executing means(11) so that the motor-operated expansion valve (5) holds for a set timea fully closed state after opened and closed. In detail, thesuperheating control means (14) activates the timer for one minute afterthe output of the opening and closing signals and prohibits the secondand later times opening/closing operations until one minute passes.

The operation shifting means (15) executes the shift from defrostingoperation to heating cycle operation when the defrosting executing means(11) completes defrosting operation, so as to control the open/shut-offvalve (SV) to hold it open for a set time in a heating cycle and thenturn it closed while controlling the motor-operated expansion valve (5)to gradually open it to a specified opening. In detail, the operationshifting means (15) opens the open/shut-off valve (SV) for two minutesafter the completion of defrosting operation and then closes it, whileexecuting gradually opening control of the motor-operated expansionvalve (5) for three minutes after the completion of defrosting operationin such a manner as to once open the motor-operated expansion valve (5)of a fully closed state to 80 pulses, hold it in the partially openedstate for 10 seconds, and then open it by 2 pulses in every five secondsor open it by 1 pulse in every 10 seconds when the outdoor-airtemperature Ta is 23° C. or less.

Defrosting operation in Embodiment 1

Next, description will be made about controls of defrosting operation ofthe air conditioner above-mentioned, with reference to a timing chart ofFIG. 4.

First, in heating cycle operation, the four-way selector valve (2) isturned to an ON state as shown from a point a to point b, that is,switched to the broken line shown in FIG. 2, to fuzzy-control theopening of the motor-operated expansion valve (5) and the frequency stepN of the compressor (1) so as to be an optimum discharge-pipetemperature, thereby performing heating operation.

At the point b, the controller (10) outputs a defrosting requiringsignal according to a mean value of heating performance. When thedefrosting requiring signal is outputted, defrosting operation waitsuntil preparation of defrosting operation in the indoor unit (B) iscompleted at a point c, e.g., until treatment on a heater or the like iscompleted, the low-pressure-control pressure switch (LPS) is masked andthen defrosting operation further waits for 35 seconds to a point d,i.e., to the time that the frequency step N of the compressor (1) toswitch the four-way selector valve (2), which is 6, comes.

Thereafter, from the point d, fully closing operation for making theopening of the motor-operated expansion valve (5) into 0 pulse isstarted and liquid refrigerant stored in the outdoor heat exchanger (3)is recovered. When the time sufficient for fully closing themotor-operated expansion valve (5) has passed, the indoor fan (6f) isdeactivated at a point e and heat storage in the indoor heat exchanger(6) is executed with high-pressure refrigerant.

This heat storage operation is completed when it has been executed forat most 10 seconds, when the indoor heat-exchange temperature Te risesabove 35° C., when the outdoor heat-exchange temperature Tc drops below-30° C., or when the present outdoor heat-exchange temperature Tc drops4° C. more than the outdoor heat-exchange temperature Tc at the timebefore the heat storage is started (See a point f).

At this point f, the defrosting executing means (11) deactivates theoutdoor fan (3f), switches the four-way selector valve (2), i.e.,switches according to the defrosting requiring signal the four-wayselector valve (2) as shown in the solid line of FIG. 2 to set it to acooling cycle, and feeds to the outdoor heat exchanger (3)high-temperature refrigerant discharged from the compressor (1) to startdefrosting operation in the reverse cycle.

As a feature of this invention, when the defrosting operation isstarted, the defrosting executing means (11) ordinarily closes themotor-operated expansion valve (5) into a fully closed state of 0 pulseand opens the open/shut-off valve (SV), thereby shutting off the commonpassage (8a) and opening the bypass passage (4a). However, since theinitial control means (12) outputs an initially closing signal, theopen/shut-off valve (SV) is closed so that the common passage (8a) andthe bypass passage (4a) are shut off until 15 seconds passes.

In detail, switching of the four-way selector valve (2) reverses thepressure distribution of refrigerant in the refrigerant circuit (9) tomake the refrigerant pressure in the receiver (4) higher than therespective refrigerant pressures in the outdoor heat exchanger (3) andthe indoor heat exchanger (6). If under such conditions themotor-operated expansion valve (5) and the open/shut-off valve (SV)remain opened, liquid refrigerant of high-temperature and high-pressureflows through the outdoor heat exchanger (3) and the indoor heatexchanger (6). Further, in such a case, liquid refrigerant is evaporatedin the indoor heat exchanger (6), and refrigerant thus evaporated expelsliquid refrigerant from the indoor heat exchanger (6) so that liquidrefrigerant excessively flows into the compressor (1), while liquidrefrigerant flowing into the outdoor heat exchanger (3) reduces acondensation area. As a result, defrosting performance is reduced. Tosolve this problem, as mentioned above, the motor-operated expansionvalve (5) and the open/shut-off valve (SV) are closed thereby preventingthe discharge of liquid refrigerant from the receiver (4).

Thereafter, when 15 seconds has passed, the defrosting executing means(11) opens the open/shut-off valve (SV) at a point g to execute ordinarydefrosting operation and gradually increases the operational frequency Nof the compressor (1).

Then, refrigerant discharged from the compressor (1) is condensed in theoutdoor heat exchanger (3) to dissolve frost and flows into the receiver(4). From the receiver (4), gas refrigerant flows into the indoor heatexchanger (6) via the bypass passage (4a) and returns to the compressor(1). By such circulation of refrigerant, defrosting operation isexecuted.

Subsequently, when the discharge-pipe temperature Td rises above 90° C.in the defrosting operation, between a point h and a point i thesuperheating control means (14) outputs respective signals for openingand closing the motor-operated expansion valve (5) to once open themotor-operated expansion valve (5) to 200 pulses and then close it. Indetail, gas refrigerant is discharged from the receiver (4) and flowsthrough the bypass passage (4a). However, in the case of defrosting at ahigh open-air temperature or the case of long refrigerant piping, itreadily becomes short of refrigerant so that the compressor (1) causesoperation in superheated condition thereby increasing the discharge-pipetemperature Td.

To cope with this problem, the superheating control means (14) onceopens the motor-operated expansion valve (5) to introduce liquidrefrigerant in the receiver (4) into the indoor heat exchanger (6)through the downstream-side common passage (8Y) as shown in FIG. 3,thereby preventing the operation in superheated condition.

The opening/closing operation of the motor-operated expansion valve (5)is executed a single time in every one minute. In detail, as shown in aterm j, after outputting an opening signal and a closing signal, thesuperheating control means (14) outputs a full-close holding signal sothat the motor-operated expansion valve (5) holds for one minute thefully closed state after opened and closed, thereby prohibiting theexcessive opening/closing operation.

On the other hand, when the discharge-pipe temperature Td drops below85° C. in the defrosting operation, between a point k and a point l thewet condition control means (13) outputs a closing signal for theopen/shut-off valve (SV) to hold the open/shut-off valve (SV) closed for20 seconds. In detail, gas refrigerant is discharged from the receiver(4) and flows through the bypass passage (4a). However, if the receiver(4) is filled with liquid refrigerant, liquid refrigerant turns back tothe compressor (1) through the indoor heat exchanger (6) so that thecompressor (1) operates in wet condition, thereby decreasing thedischarge-pipe temperature Td. To cope with this problem, the wetcondition control means (13) closes the open/shut-off valve (SV) andshuts off the common passage (8a) and the bypass passage (4a) to preventliquid refrigerant from turning back, thereby preventing the operationin wet condition.

The closing operation of the open/shut-off valve (SV) is executed asingle time in every 50 seconds. In detail, as shown in a term m, afteroutputting a closing signal, the wet condition control means (13)outputs an opening holding signal so that the open/shut-off valve (SV)holds for 50 seconds the opened state after closed, thereby prohibitingthe excessive closing operation.

Thereafter, in any one of the case that the frequency step N of thecompressor (1) drops to 6, the case that the discharge-pipe temperatureTd rises above 110° C., and the case that the defrosting operationperiod becomes longer than 10 minutes, as shown in a point n, thedefrosting executing means (11) completes defrosting operation, turnsthe four-way selector valve (2) to an ON state to switch it as shown inthe broken line of FIG. 2 and activates the outdoor fan (3f), therebystarting heating operation in a hot start. At the time just before thedefrosting operation is completed, the frequency step N of thecompressor (1) is set to become 6 without exception according to thetimer or the discharge-pipe temperature Td.

Then, when the defrosting operation is completed, between a point n anda point o the operation shifting means (15) opens the open/shut-offvalve (SV) for 2 minutes and then closes it to prevent the short ofrefrigerant, while between the point n and a point p the operationshifting means (15) gradually opens the motor-operated expansion valve(5) to prevent the operation in wet condition. In detail, the operationshifting means (15) first opens the motor-operated expansion valve (5)in a partially opened state of 80 pulse, holds it in this state for 10seconds, then opens the motor-operated expansion valve (5) by 2 pulsesin every 5 seconds or opens it by 1 pulse in every 10 seconds in thecase of the outdoor-air temperature Ta of 23° C. or less, andfuzzy-controls the opening of the motor-operated expansion valve (5) andthe frequency step N of the compressor (1) so as to become the optimumdischarge-pipe temperature, thereby restarting normal heating operation.

Characteristic Effects of Embodiment 1

According to the present embodiment, since the open/shut-off valve (SV)is opened in defrosting operation so that gas refrigerant in thereceiver (4) is introduced into the main line (9a) via the bypasspassage (4a), when liquid refrigerant condensed in the outdoor heatexchanger (3) is stored in the receiver (4) in the case of heavy frost,low open-air temperature or short refrigerant piping, liquid refrigerantin the receiver (4) can be securely prevented from turning back to thecompressor (1) without provision of any accumulator. As a result,operation in wet condition of the compressor (1) can be securelyprevented so that the compressor (1) is subjected to no stress, therebyenhancing reliability of the compressor (1).

Further, since no accumulator is needed, pressure loss can be decreasedthereby enhancing operation performance, and the number of elements canbe reduced thereby resulting in cost reduction.

Furthermore, since the motor-operated expansion valve (5) and theopen/shut-off valve (SV) are closed at the initial stage of thedefrosting operation, it can be securely prevented that liquidrefrigerant in the receiver (4) flows into the outdoor heat exchanger(3) and the indoor heat exchanger (6) due to variation in pressure ofthe refrigerant circuit caused by switching the four-way selector valve(2). Thus, turning back of liquid refrigerant to the compressor (1) canbe prevented and a condensation area in the outdoor heat exchanger (3)can be sufficiently ensured, so that defrosting performance can beincreased.

Further, since the open/shut-off valve (SV) is closed when thedischarge-pipe temperature Td drops in the defrosting operation, liquidrefrigerant on a suction side of the compressor (1) can be evaporated.Consequently, turning back of liquid refrigerant can be prevented sothat operation in wet condition of the compressor (1) can be securelyprevented, thereby further enhancing reliability of the compressor (1).

Furthermore, since the open/shut-off valve (SV) once closed is held inan opened state for a set time, the compressor (1) can be prevented inadvance from operating in superheated condition due to frequent closingcontrol of the open/shut-off valve (SV).

Further, since the motor-operated expansion valve (5) is opened when thedischarge-pipe temperature Td rises in the defrosting operation, liquidrefrigerant is turned back to cool down superheated refrigerant on asuction side of the compressor (1), so that operation in superheatedcondition of the compressor (1) can be securely prevented therebyfurther enhancing reliability of the compressor (1).

Furthermore, since the motor-operated expansion valve (5) is once openedand is then held in a fully closed state for a set time, the compressor(1) can be prevented in advance from operating in wet condition due tofrequent opening/closing control of the motor-operated expansion valve(5). In other words, the wet condition control means (13) and thesuperheating control means (14) hold the discharge-pipe temperature Tdin an optimum temperature so that the compressor (1) is subjected to nostress.

Moreover, when the defrosting operation is completed, the open/shut-offvalve (SV) is opened and the motor-operated expansion valve (5) isgradually opened. Since this ensures the minimum circulation amount ofrefrigerant at the shift to heating operation, heating performance canbe increased. Further, since turning back of liquid refrigerant to thecompressor (1) can be prevented, operation in wet condition of thecompressor (1) can be prevented while dilution of lubricating oil in thecompressor (1) can be prevented.

Modification of Embodiment 1

FIG. 5 shows a motor-operated valve (V1) freely adjustable in opening,which is substituted for the open/shut-off valve (SV) of the aboveembodiment. Other structure, operations and effects are the same as inthe above embodiment. The opening of the motor-operated valve (V1) maybe controlled into a fully opened state and a fully closed state, or maybe otherwise adjusted according to the discharge-pipe temperature Td orthe like.

Embodiment 2

FIG. 6 shows another embodiment of the invention. In the presentembodiment, a three way valve (V2) is substituted for the open/shut-offvalve (SV) of the above embodiment, and the bypass passage (4a) isconnected to a high-pressure side of the motor-operated expansion valve(5).

The three way valve (V2) forms a selector means switchable between abypass communication state in which the high-pressure side of themotor-operated expansion valve (5) is communicated with the bypasspassage (4a) and a main line communication state in which thehigh-pressure side of the motor-operated expansion valve (5) iscommunicated with the common passage (8a) of the main line (9a).

Structure and Operation of Defrosting Operation Control of Embodiment 2

Description will be made about the structure and operations ofdefrosting operation control in an embodiment of FIG. 6, with referenceto the timing chart of FIG. 4.

First, when the defrosting executing means (11A1) starts defrostingoperation at a point f, it switches the four-way selector valve (2) asshown in the solid line of FIG. 6 and switches the three way valve (V2)as shown in the broken line of. FIG. 6, so that the bypass passage (4a)is communicated with the motor-operated expansion valve (5) therebyresulting in the bypass communication state. Further, the initialcontrol means (12A1) controls the motor-operated expansion valve (5) tohold it in a fully closed state for 15 seconds in correspondence withthe closure of the open/shut-off valve (SV) in the before-mentionedembodiment (See points f to g of FIG. 4).

Thereafter, the motor-operated expansion valve (5) is opened at aspecified opening and is held in the specified opening, so that gasrefrigerant in the receiver (4) is introduced toward the indoor heatexchanger (6) through the bypass passage (4a) thereby executingdefrosting operation. When the discharge-pipe temperature Td rises above90° C. in the defrosting operation, the superheating control means(14A1) outputs a switching signal to switch the three way valve (V2) asshown in the solid line of FIG. 6 thereby forming the main linecommunication state. Then, the superheating control means (14A1)switches again the three way valve (V2) as shown in the broken line ofFIG. 6 thereby forming the bypass communication state, and subsequentlyoutputs a switching holding signal to hold the bypass communicationstate for a set time (See points h to i and a term j of FIG. 4). Inother words, because the compressor (1) is on its way to superheatedcondition, operation in superheated condition is prevented by theintroduction of liquid refrigerant in the receiver (4) toward the indoorheat exchanger (6).

On the other hand, when the discharge-pipe temperature Td drops below85° C., the wet condition control means (13A1) outputs a fully closingsignal to make the motor-operated expansion valve (5) fully closed for20 seconds, and subsequently outputs a full-close holding signal to holdthe motor-operated expansion valve (5) in a specified opened state for30 seconds (See points k to l and a term m of FIG. 4). In other words,because the compressor (1) is on its way to wet condition, the commonpassage (8a) and the bypass passage (4a) are shut off together therebypreventing the operation in wet condition.

Thereafter, when the defrosting operation is completed (See a point n ofFIG. 4), the four-way selector valve (2) is switched as shown in thebroken line of FIG. 6 and the three way valve (V2) is switched as shownin the solid line of FIG. 6 so that the main line communication state isformed, while the motor-operated expansion valve (5) is opened to atarget opening. Thus, normal heating operation is restarted.

Other structure and operations are the same as in the before-mentionedembodiment. Accordingly, in the present embodiment, similar to thebefore-mentioned embodiment, operation in wet condition and operation insuperheated condition of the compressor (1) can be securely preventedwithout any accumulator, thereby enhancing operation performance andreliability of the compressor (1).

Embodiment 3

FIG. 7 shows another embodiment of the invention. In the presentembodiment, the bypass passage (4a) is connected to a low-pressure sideof the motor-operated expansion valve (5) instead of being connected tothe high-pressure side of the motor-operated expansion valve (5) in theabove embodiment of FIG. 6.

The three way valve (V2) forms a selector means switchable between abypass communication state in which the down-stream-side common passage(8Y) is communicated with the bypass passage (4a) and a main linecommunication state in which the downstream-side common passage (8Y) iscommunicated with the common passage (8a).

Structure and Operation of Defrosting Operation Controls of Embodiment 3

Description will be made about the structure and operations ofdefrosting operation control in an embodiment of FIG. 7, with referenceto the timing chart of FIG. 4.

First, when the defrosting executing means (11A2) starts defrostingoperation at a point f, it switches the four-way selector valve (2) asshown in the solid line of FIG. 7 and switches the three way valve (V2)as shown in the broken line of FIG. 7, so that the bypass passage (4a)the bypass passage (4a) is communicated with the downstream-side commonpassage (8Y), thereby resulting in the bypass communication state.Further, the initial control means (12A2) holds the three way valve (V2)in the main line communication state shown in the solid line of FIG. 7while controlling the motor-operated expansion valve (5) to hold it in afully closed state for 15 seconds in correspondence with the closure ofthe open/shut-off valve (SV) in the before-mentioned embodiment (Seepoints f to g of FIG. 4).

Thereafter, the defrosting executing means (11A2) switches the three wayvalve (V2) as shown in the broken line of FIG. 7 to form the bypasscommunication state, so that gas refrigerant in the receiver (4) isintroduced toward the indoor heat exchanger (6) through the bypasspassage (4a) thereby executing defrosting operation. When thedischarge-pipe temperature Td rises above 90° C. in the defrostingoperation, the superheating control means (14A2).outputs a switchingsignal to switch the three way valve (V2) as shown in the solid line ofFIG. 7 thereby forming the main line communication state, and opens themotor-operated expansion valve (5) to a specified opening. Then, thesuperheating control means (14A2) switches again the three way valve(V2) as shown in the broken line of FIG. 7 thereby forming the bypasscommunication state, and subsequently outputs a switching holding signalto hold the bypass communication state for a set time (See points h to iand a term j of FIG. 4). In other words, because the compressor (1) ison its way to superheated condition, operation in superheated conditionis prevented by the introduction of liquid refrigerant in the receiver(4) toward the indoor heat exchanger (6).

On the other hand, when the discharge-pipe temperature Td drops below85° C., the wet condition control means (13A2) outputs a switchingsignal to switch the three way valve (V2) as shown in the solid line ofFIG. 7 thereby forming the main line communication state, and makes themotor-operated expansion valve (5) fully closed for 20 seconds. Then,the wet condition control means (13A2) switches again the three wayvalve (V2) as shown in the broken line of FIG. 7 thereby forming thebypass communication state, and subsequently outputs a switching holdingsignal to hold the bypass communication state for a set time (See pointsk to l and a term m of FIG. 4). In other words, because the compressor(1) is on its way to wet condition, the common passage (8a) and thebypass passage (4a) are shut off together thereby preventing theoperation in wet condition.

Thereafter, when the defrosting operation is completed (See a point n ofFIG. 4), the four-way selector valve (2) is switched as shown in thebroken line of FIG. 7 and the three way valve (V2) is switched as shownin the solid line of FIG. 7 so that the main line communication state isformed, while the motor-operated expansion valve (5) is opened to atarget opening. Thus, normal heating operation is restarted.

Other structure and operations are the same as in the before-mentionedembodiment of FIG. 2. Accordingly, in the present embodiment, similar tothe before-mentioned embodiment, operation in wet condition andoperation in superheated condition of the compressor (1) can be securelyprevented, thereby enhancing reliability of the compressor (1).

Embodiment 4

FIG. 8 shows another embodiment of this invention. In the presentembodiment, a capillary (CP) is provided instead of the open/shut-offvalve (SV) of the embodiment of FIG. 2.

Accordingly, in defrosting operation, the motor-operated expansion valve(5) is fully closed so that gas refrigerant in the receiver (4) flowsthrough the bypass passage (4a).

Other Modifications

In the above embodiments, operation control of the compressor (1) in wetcondition and in superheated condition in defrosting operation isexecuted in such a manner that the open/shut-off valve (SV), themotor-operated expansion valve (5) and the like are opened and closed.However, the bypass passage (4a) may be communicated at any time duringdefrosting operation.

Further, the compressor (1) may be controlled based on a pressure ofrefrigerant on the discharge side.

Furthermore, the refrigerant circuit (9) is not limited to the aboveembodiments. For example, it may be a refrigerant circuit having norectification circuit (8r).

INDUSTRIAL APPLICABILITY

As described so far, an operation control device for air conditioner ofthis invention is useful for air conditioners having no accumulator.

We claim:
 1. In an air conditioner comprising a refrigerant circuit (9)which has a main line (9a) in which a compressor (1), athermal-source-side heat exchanger (3), an expansion mechanism (5)freely adjustable in opening and a used-side heat exchanger (6) aresequentially connected, said refrigerant circuit (9) being reversiblyoperable between cooling cycle operation and heating cycle operation, anoperation control device for said air conditioner comprising:a receiver(4) for storing liquid refrigerant, said receiver being provided in ahigh-pressure liquid line of the main line (9a) of the refrigerantcircuit (9); a bypass passage (4a) for bypassing the expansion mechanism(5) to introduce gas refrigerant in the receiver (4) into a low-pressureliquid line of the main line (9a) of the refrigerant circuit (9), saidbypass passage (4a) being connected at one end thereof to the receiver(4) and at the other end to the low-pressure liquid line; open/shut-offmeans (SV) for opening and shutting off the bypass passage (4a), saidopen/shut-off means (SV) being provided in the bypass passage (4a); anddefrosting executing means (11) for making the expansion mechanism (5)fully closed and making the open/shut-off means (SV) open according to adefrosting requiring signal in the heating cycle operation and executingdefrosting operation in the reverse cycle.
 2. An operation controldevice for air conditioner according to claim 1, furthercomprisinginitial control means (12) for outputting an initially closingsignal to the defrosting executing means (11) so that the open/shut-offmeans (SV) is closed until a set time passes after the start of thedefrosting operation.
 3. An operation control device for air conditioneraccording to claim 1, further comprisingwet condition control means (13)for outputting a closing signal to the defrosting executing means (11)so that the open/shut-off means (SV) is closed when a refrigeranttemperature on a discharge side of the compressor (1) drops to or belowa specified temperature.
 4. An operation control device for airconditioner according to claim 3, whereinthe wet condition control means(13) outputs a closing signal to the defrosting executing means (11) sothat the open/shut-off means (SV) becomes an opened state after holdinga closed state for a set time, and then outputs an opening holdingsignal to the defrosting executing means (11) so that the open/shut-offmeans (SV) holds the opened state for a set time after closed.
 5. Anoperation control device for air conditioner according to claim 1,further comprisingsuperheating control means (14) for outputtingrespective signals for opening and closing the motor-operated expansionvalve (5) to the defrosting executing means (11) so that when arefrigerant temperature on a discharge side of the compressor (1) risesto or above a specified temperature, the expansion mechanism (5) isopened to a specified opening and then closed into a fully closed state.6. An operation control device for air conditioner according to claim 5,whereinthe superheating control means (14) outputs a full-closingholding signal to the defrosting executing means (11) so that theexpansion mechanism (5) holds the fully closed state for a set timeafter opened and closed.
 7. An operation control device for airconditioner according to any one of claims 1 to 6, furthercomprisingoperation sifting means (15) for shifting the circuit to theheating cycle operation when the defrosting executing means (11)completes the defrosting operation, so as to control the open/shut-offmeans (SV) to hold it open for a set time in a heating cycle and thenturn it closed while controlling the expansion mechanism (5) togradually open it to a specified opening.